Nasal cannula assembly with inhalation valves communicating with a deformable reservoir

ABSTRACT

The invention concerns a nasal cannula assembly ( 10 ) adapted to deliver gases to a patient comprising a first compartment ( 1 ) and a second compartment ( 2 ) separated by a separation wall ( 6 ); a pair of nasal prongs ( 5 ) in fluid communication with the first compartment ( 1 ); the first compartment ( 1 ) comprising a first inlet ( 11 ) for introducing a first gas into said first compartment ( 1 ); the second compartment ( 2 ) comprising a second inlet ( 2 ) for introducing a second gas into said second compartment ( 2 ); and the separation wall ( 6 ) comprising at least one valve element ( 3 ) for controlling the passage of gas from the second compartment ( 2 ) to the first compartment ( 1 ). The invention concerns also a breathing assistance apparatus comprising a source of NO gas, and said nasal cannula assembly ( 10 ) in fluid communication with said source of NO gas.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns a nasal cannula assembly adapted to deliver gasesto a patient, especially for NO gas therapy, a breathing assistanceapparatus comprising such a nasal cannula assembly, and a method fortreating pulmonary vasoconstriction in a patient using such a nasalcannula assembly and/or breathing assistance apparatus.

2. Description of the State of the Art

NO/nitrogen gas mixtures are commonly used for treatingvasoconstrictions of the lung and pulmonary hypertension in adults andinfants.

For instance, EP-A-1516639 discloses a gaseous mixture consisting of NOand an inert gas, preferably nitrogen, used for the production of aninhalable medicament for treating persistent pulmonary hypertension ofthe newborn.

Before being inhaled by the patient, the NO/N₂ mixture is generallydiluted in an oxygen-containing gas, such as air or a O₂/N₂ mixture,comprising at least 21 vol. % of oxygen.

Typically, NO is present in the final mixture in an amount of several(1-800, most often 5- 80) ppm in volume.

However, as NO is rapidly oxidized into NO₂ in the presence of oxygen,it is important to avoid long residence times in gas administrationapparatus between the point of mixing of the NO/N₂ mixture with theoxygen containing gas and inhalation by the patient, in order to keepthe concentration of NO₂ in said inhalable medicament at less than 5ppm, ideally less than 1 ppm, in the inhaled gas mixtures because NO₂ isa highly toxic gas.

NO gas mixtures are delivered by modified ventilation devices or specialmodules added to standard ventilators. Such devices are well known andtaught, for instance, by U.S. Pat. Nos. 5,558,083; 5,873,359; 5,732,693;and 6,051,241.

Current NO delivery systems are designed for use with ventilators orother breathing gas delivery devices in a hospital or transport setting.Systems to deliver NO to ambulatory patients are in development. Themajority of delivery devices are pulsed, sequential, or proportionaldelivery systems that sense the start of patient inhalation and use oneor more electronically controlled valves or switches to deliver asequenced flow of NO to the patient interface, for example anendotracheal tube, a facemask, or a nasal cannula.

For example, U.S. Pat. No. 6,089,229 discloses a device comprisingsensing means for sensing the initiation of an inhalation of a patientand a delivery means responsive to the sensing means.

Further, U.S. Pat. No. 6,142,147 teaches an apparatus with a pressuresensor and a valve controller which is responsive to the pressuresensor, and which selectively connects a first port to a second port,said second port being connected to a source of NO gas, when a negativepressure event is sensed. Here the negative pressure event would becaused by a patient's inhalation so that again a means of sensing thepatient's inhalation is used.

Furthermore, U.S. Pat. No. 6,581,599 deals with a method of deliveringNO that includes detecting the onset of inspiration.

If adapted for NO delivery to ambulatory patients, such systems sufferfrom the requirements of a source of electrical power and the need forelectromechanical parts to sense and administer sequenced pulses of NO,both of which increase the size of the system, and limit itsportability. In addition, due to inevitable lags in timing betweendetection of the start of patient inhalation and operation of dosingvalves, these systems risk delivering their pulses too late in theinhalation, such that a significant fraction of NO is exhaled.

However, there is sufficient evidence to suggest that long term NOtherapy may be beneficial for some therapeutic indications, e.g. intreating pulmonary arterial hypertension. For these long term therapies,alternative delivery systems are needed for ambulatory patients. This iscomparable to the need for devices for outpatient and in-home oxygentherapy.

For this purpose, a delivery system convenient for use by ambulatorypatients, requiring a minimum of electromechanical parts, is required sothat they can follow their NO treatment after they have left thehospital setting.

One common patient interface for home oxygen delivery is a standard formnasal cannula. Nasal cannulas are well known and widely used to deliversupplemental oxygen to patients suffering from a wide variety ofrespiratory and cardiovascular diseases. Generally, one end of an oxygensupply tubing is connected to a source of oxygen, and the other end ofthe tubing splits into two branches that meet to form a loop, where aset of two nasal prongs are positioned on that loop. The nasal prongsare inserted into a patient's nares, and a constant or time-pulsed flowof oxygen regulated by the source is sent through the tubing and the twobranches of the loop so as to exit through the nasal prongs into thepatient's nares. During inspiration, the patient inhales oxygen from theprongs together with entrained room air that is drawn through the spacebetween the nasal prongs and the walls of the patient's nares. Duringexhalation, the patient exhales through the space between the nasalprongs and the walls of the patient's nares, and in the case of aconstant oxygen supply flow, oxygen continues to exit into the patient'snares, such that much of this oxygen is carried with the expiratory flowinto the surrounding room air. Pulsed oxygen delivery devices attempt toconserve oxygen by sensing the patient's breathing cycle, and thendelivering a short-duration flow or pulse of oxygen through a nasalcannula only during inhalation, so as to avoid losing oxygen to the roomair during exhalation.

As nasal cannulas are standard in the delivery of supplemental oxygen,many variants exist. For example, U.S. Pat. No. 4,535,767 to Tiep et al.describes an oxygen delivery apparatus consisting of a reservoircannula, a version of which is available as a commercial product calledthe Oxymizer from Chad Therapeutics, as described, for example by Dumontand Tiep (Using a reservoir nasal cannula in acute care; Crit Care Nurse2002;22:41-46). This reservoir cannula includes a chamber in fluidcommunication with both the oxygen supply line and nasal prongs. Thechamber is enclosed in part by a flexible diaphragm that collapses uponinhalation so as to empty its contents through the nasal prongs while atthe same time blocking flow from the oxygen supply line to the chamber.The flexible diaphragm then expands during exhalation to fill thechamber with exhaled gas while re-establishing flow from the oxygensupply line into the chamber, such that oxygen from the supply linemixes with and displaces the exhaled gas through the nasal prongs. Thistype of reservoir cannula has found utility in supplying supplementaloxygen to patients, but is ill-suited for supplying patients withNO/nitrogen gas mixtures in place of oxygen. First, reservoir cannulasas previously described contain means to connect to only a single sourceof gas; however because commercial NO/nitrogen gas mixtures contain nooxygen, patients may require an additional source of supplementaloxygen. Second, even if air entrained from the room during inhalationprovides sufficient oxygen to meet a patient's demand, it is notacceptable that oxygen-containing gas exhaled by the patient mix withNO-containing gas supplied to the chamber. It is well known that NO andoxygen react over time to produce NO₂, which is toxic even at relativelylow concentrations (e.g. above 5 ppm short term or even 1 ppm for longterm), and as such it is well accepted that the residence time duringwhich NO is brought into contact with oxygen should be minimized whensupplying these gases to a patient. Finally, the Oxymizer cannuladelivers 20 mL of oxygen to the patient each breath. For commonlysupplied concentrations of medical NO/nitrogen gas mixutres (e.g.containing 800 ppm NO in balance nitrogen) this delivered volume risksexposing the patient to too high a concentration of NO and too low aconcentration of oxygen, especially for younger patients with tidalvolumes less than ˜200 ml, or for adult patients exhibiting rapid,shallow breathing.

Another nasal cannula variant that exists is commonly referred to as adual-lumen nasal cannula. For example TeleFlex Hudson RCI Dual LumenCannulas are commercially available. These cannulas connect throughtubing to a source of oxygen and to a pressure sensing instrument, bothof which are in fluid communication with a pair of nasal prongs, thecross section of each prong being split into two sections (or lumen) bya wall, with one section in fluid communication with the source ofoxygen, and the other section in fluid communication with the pressuresensing instrument. While it is possible that one could conceive ofconnecting a source of NO-containing gas in place of the pressuresensing instrument in order to supply both NO and oxygen simultaneouslythrough the dual-lumen cannula, no reservoir, chamber, or othermechanism is included to control the flow of gases. To provide a pulseddelivery of NO, one would need to rely on the systems described abovethat sense the start of patient inhalation and use one or moreelectronically controlled valves or switches to deliver a sequencedpulse of NO.

BRIEF SUMMARY OF THE INVENTION

A main goal of the invention is to provide a delivery system convenientfor use by ambulatory patients, which allows nitric oxide (NO) to beefficiently administered over extended time periods, i.e. hours, days,weeks, through nasal prongs in a manner that minimizes delivery into theanatomical dead volume at the end of inhalation, and therefore alsominimizes exhalation of NO. In so doing, the system must avoid bringingNO-containing gas into contact with oxygen-containing gas until justprior to delivery to the patient, so as to avoid or minimize productionof toxic NO₂ gas through reaction of NO with oxygen.

Another goal is to provide a delivery system that, in contrast to pulseddelivery systems described in prior art, does not require a sensor todetect the onset of inspiration nor any processing unit (such as a PLCor programmable computer) or other electronics.

A solution according to the present invention concerns a nasal cannulaassembly adapted to deliver gases to a patient comprising:

a first compartment and a second compartment separated by a separationwall,

a pair of nasal prongs in fluid communication with the firstcompartment,

the first compartment comprising a first inlet for introducing a firstgas into said first compartment,

the second compartment comprising a second inlet for introducing asecond gas into said second compartment, and

the separation wall comprising at least one valve element forcontrolling the passage of gas from the second compartment to the firstcompartment.

Depending on the embodiment, the nasal cannula assembly according to thepresent invention can comprise one or several of the following features:

the separation wall comprises at least two valve elements.

the first compartment comprises a first inlet forming a side gases entryin fluid communication with a gas transport conduct.

the nasal cannula assembly further comprises a hollow body comprising aninternal chamber comprising at least the first compartment.

at least the first compartment is part of a hollow body forming a gasconduct or a manifold.

said hollow body and said pair of nasal prong are integrally molded froma soft plastics material.

the prongs are detachable from said hollow body to allow different sizedprongs to be placed on said hollow body to suit different sizedpatients.

the valve element(s) are one-way valve(s).

a pair of valve elements is arranged in the separation wall, directlyopposite the pair nasal prongs.

the second compartment comprises a deformable wall.

the second compartment forms a deformable-wall reservoir comprising aninternal volume for the gas, when fully inflated, of about 0.5 to 5 ml.

The present invention also concerns a breathing assistance apparatuscomprising:

a source of NO-containing gas, and

a nasal cannula assembly according to the present invention in fluidcommunication with said source of NO-containing gas.

Depending on the embodiment, the breathing assistance apparatusaccording to the present invention can comprise one or several of thefollowing features:

breathing assistance apparatus further comprises a source of anoxygen-containing gas in fluid communication with the nasal cannulaassembly.

said source of NO-containing contains NO and nitrogen.

said source of NO-containing contains up to 3000 ppm in volume of NO ina balance of nitrogen.

The present invention also concerns a method for treating pulmonaryvasoconstriction in a patient, comprising:

a) providing a nasal cannula assembly according to the presentinvention, and

b) providing a therapeutically-effective amount of a NO-containing gasto said patient through said nasal cannula assembly for inhalation.

Depending on the embodiment, the nasal cannula assembly according to thepresent invention can comprise one or several of the following features:

the patient is an adult, an infant or a newborn.

pulmonary vasoconstriction is associated with persistent pulmonaryhypertension of the newborn.

pulmonary vasoconstriction is associated with pulmonary arterialhypertension.

the NO-containing gas is mixed with an oxygen-containing gas just beforebeing inhaled by the patient.

the NO-containing gas is a NO/nitrogen mixture.

the NO-containing gas consists in a NO/nitrogen mixture containing up to3000 ppm by volume of NO.

the O₂-containing gas is air or an O₂/N₂ mixture containing at least 21vol. % of O₂.

The invention may be further defined in some embodiments by one or moreof the following numbered sentences:

1. A nasal cannula assembly (10) adapted to deliver gases to a patient,the nasal cannula assembly (10) comprising:

a) a hollow body (4) configured to be capable of acting as a gas conductor a gas manifold and comprising an internal chamber (7) defining afirst compartment (1),

b) the first compartment (1) and a second compartment (2) separated by aseparation wall (6),

c) a pair of nasal prongs (5) in fluid communication with the firstcompartment (1),

d) the first compartment (1) comprising a first inlet (11) forming aside gases entry in fluid communication with a gas transport conduct andconfigured to conduct a first gas into said first compartment (1),

e) the second compartment (2) having a fully inflated internal volumefor a gas of about 0.5 to 5 ml, the second compartment (2) comprising,

-   -   a second inlet (12) configured to conduct a second gas into said        second compartment (2), and    -   a deformable wall (14) having a greater Compliance while filling        than when the second compartment (2) is full,

f) the separation wall (6) comprising at least two, one-way, duckbill orumbrella valves (3) having a cracking pressure of 0.5 kPa or less whichare oriented and arranged in the separation wall (6) directly oppositethe pair nasal prongs (5) to thereby be capable of

-   -   permitting a passage of gas from the second compartment (2) to        the first compartment (1) and    -   preventing or limiting a passage of gas from the first        compartment (1) to the second compartment (2).        2. A nasal cannula assembly (10) adapted to deliver gases to a        patient, the nasal cannula assembly (10) comprising:

a) a first compartment (1) and a second compartment (2) separated by aseparation wall (6),

b) a pair of nasal prongs (5) in fluid communication with the firstcompartment (1),

c) the first compartment (1) comprising a first inlet (11) configured toconduct a first gas into said first compartment (1),

d) the second compartment (2) comprising a second inlet (12) configuredto conduct a second gas into said second compartment (2), and

e) the separation wall (6) comprising at least one valve element (3)configured to

-   -   permit a passage of gas from the second compartment (2) to the        first compartment (1) and    -   prevent or limit a passage of gas from the first compartment (1)        to the second compartment (2).        3. The nasal cannula assembly according to Numbered Sentence 1        or 2, wherein the separation wall (6) comprises at least two        valve elements (3).

4. The nasal cannula assembly according to Numbered Sentence 1, 2 or 3,wherein the first compartment (1) comprises a first inlet (11) forming aside gases entry in fluid communication with a gas transport conduct.

5. The nasal cannula assembly according to Numbered Sentence 1, 2, 3 or4, wherein the nasal cannula assembly further comprises a hollow body(4) comprising an internal chamber (7) comprising at least the firstcompartment (1).6. The nasal cannula assembly according to Numbered Sentence 1, 2, 3, 4or 5, wherein at least the first compartment (1) is part of a hollowbody (4) configured to be capable of acting as a gas conduct or a gasmanifold.7. The nasal cannula assembly according to Numbered Sentence 1, 2, 3, 4,5 or 6, wherein said hollow body (4) and said pair of nasal prong (5)are integrally molded from a soft plastics material.8. The nasal cannula assembly according to Numbered Sentence 1, 2, 3, 4,5, 6 or 7, wherein the prongs (5) are detachable from said hollow body(4) and selected from different sized prongs suitable for differentsized patient nares.9. The nasal cannula assembly according to Numbered Sentence 1, 2, 3, 4,5, 6, 7 or 8, wherein the two valve elements (3) are one-way valves.10. The nasal cannula assembly according to Numbered Sentence 1, 2, 3,4, 5, 6, 7, 8 or 9, wherein a pair of valve elements (3) is arranged inthe separation wall (6), directly opposite the pair nasal prongs (5).11. The nasal cannula assembly according to Numbered Sentence 1, 2, 3,4, 5, 6, 7, 8, 9 or 10, wherein the second compartment (2) comprises adeformable wall (14).12. The nasal cannula assembly according to Numbered Sentence 1, 2, 3,4, 5, 6, 7, 8, 9, 10 or 11, wherein the second compartment (2) forms adeformable-wall reservoir comprising a fully inflated internal volumefor the gas of about 0.5 to 5 ml.13. The nasal cannula assembly according to Numbered Sentence 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11 or 12, wherein nasal cannula assembly does notcomprise a sensor configured to detect an onset of patient inspiration.14. The nasal cannula assembly according to Numbered Sentence 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12 or 13, wherein the valve (3) is selectedfrom an umbrella valve or a duckbill valve.15. The nasal cannula assembly according to Numbered Sentence 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, wherein the valve (3) has acracking pressure of 0.5 kPa or less.16. The nasal cannula assembly according to Numbered Sentence 11, 12,13, 14, or 15 wherein the deformable wall (14) of the second compartment(2) has a greater Compliance while filling than when the secondcompartment (2) is full.17. The nasal cannula assembly according to Numbered Sentence 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, wherein the nasalprongs (5) includes an external pillow element (8) at an end.18. The nasal cannula assembly according to Numbered Sentence 17,wherein said pillow elements (8) is made of silicone.19. The nasal cannula assembly according to Numbered Sentence 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or 18, furthercomprising an expiratory orifice (13), optionally comprising a one-wayexpiratory valve, between the first compartment (1) defining an internalchamber (7) and an external atmosphere.20. The nasal cannula assembly according to Numbered Sentence 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, furthercomprising a resistive element (9) between an internal volume (7) of thefirst compartment (1) and an air or oxygen supply (11), the resistiveelement configured to ensure a sufficient pressure drop upon the onsetof inhalation to open at least one valve element (3).21. A breathing assistance apparatus comprising:

a) a source of NO-containing gas, and

b) a nasal cannula assembly according to one or more of NumberedSentence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19 or 20, in fluid communication with said source of NO-containing gas.

22. A breathing assistance apparatus according to Numbered Sentence 21,wherein the breathing apparatus further comprises a source of anoxygen-containing gas in fluid communication with the nasal cannulaassembly.23. A breathing assistance apparatus according to Numbered Sentence 22,wherein said source of NO-containing contains NO and nitrogen.24. A breathing assistance apparatus according to Numbered Sentence 23,wherein said source of NO-containing contains from 1 ppm to 5000 ppm involume of NO in a balance of nitrogen.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention will be better understood thanks to the followingdescription and explanation made in reference to the Figures, wherein:

FIG. 1 is a schematic of a first embodiment of a nasal cannula assemblyaccording to the present invention,

FIG. 2 is a schematic of a second embodiment of a nasal cannula assemblyaccording to the present invention, and

FIG. 3 displays an estimated pattern of inhaled NO concentration thatcould be achieved using a nasal cannula assembly according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

A schematic of a first embodiment of the nasal cannula assembly of thepresent invention is shown in FIG. 1 (in cross section).

The nasal cannula assembly of the present invention is a patientinterface generally comprising a pair of nasal prongs 5 coupledindirectly to a deformable-wall 14 having a valved 3 reservoir 2supplied with NO contained in nitrogen (12), e.g. at 225, 450, 800 or1000 ppm in volume.

The pair of nasal prongs 5 is positioned on a hollow body 4, for examplean air or oxygen conduit or manifold, comprising an internal hollowvolume or chamber 7 thereby forming a first compartment 1 that receivesthe gases.

The nasal prongs 5 are small conduits or tubes adapted for insertioninto the nares of a patient and through which passes the gas mixturethat is subsequently inhaled by the patient. Each prong 5 comprises anoutlet orifice 15 at its end.

The hollow body 4 can be made of a rigid light material, such as polymeror similar. Preferably, the hollow body 4 and the pair of nasal prong 5are integrally molded from a soft plastics material. However, the prongs5 can also be detachable from said hollow body 4 to allow differentsized prongs to be placed on said hollow body 4 to suit different sizedpatients, such as adults and infants. The hollow body 4 is in turn influid communication with valved 3 reservoir 2 formed by thedeformable-wall 14 and separation wall 6. In other words, the nasalcannula assembly of the present invention is split into two main inhaledgas compartments 1 and 2 that are separated each from the other by aseparation wall 6.

The second compartment 2 forms a deformable reservoir 2 receiving the NOgas through an inlet 12. The deformable wall 14 of the reservoir orsecond compartment 2 should be made from a thin, flexible sheet ofpolymer material so that the reservoir readily inflates duringexhalation when the valves 3 are closed, but collapses, at the start ofinhalation, after the valves 3 open. In this manner, NO-containing gasis allowed to accumulate in the reservoir while the patient exhales, andthen is released as a bolus at the start of inhalation as the reservoircollapses and its contents empty through the valves 3 into the firstcompartment 1. Throughout this cycle a constant flow of NO-containinggas may be maintained through the inlet 12.

The second compartment 2 fluidly communicates with the first compartment1 through one or more fluid transfer elements such as the exemplaryone-way valves 3 which may be for instance the two umbrella valves 3shown in FIG. 1. These fluid transfer elements are arranged in theseparation wall 6. Preferably, as shown in FIG. 1, two valves 3 arepositioned along the conduit 7 forming the hollow main body 4, directlyopposite the nasal prongs 5, i.e. each valve 3 is facing one nasal prong5, so as to facilitate the gas circulation from the second compartment 2to the first compartment 1 and subsequently to the nasal prongs 5.

The fluid transfer elements may be umbrella valves, duckbill valves,valve-like conduits or flow constrictions apertures designed to permitgas flow from the second compartment 2 to the first compartment 1, butto resist flow in the opposite direction from the first compartment 1 tothe second compartment 2. In embodiments having valves 3, the valvespreferably respond to any drop in ambient pressure (i.e. due toinhalation). Ideally, valve 3 is selected to have a “cracking pressure”of zero or at least as low as is mechanically feasible. Any inhalationflow through nare tubes 5 should preferably result in valve 3 opening.

In any case, the combination of valves 3 and deformable wall 14 of theembodiment depicted in FIG. 1 should be responsive to increases anddecreases in pressure that develop during exhalation and inhalation,respectively, so as to allow the deformable reservoir 2 to inflate withNO-containing gas during exhalation, and then empty to release this gasthrough the valves 3 into the first compartment 1 during inhalation.

Generally the deformable wall 14 needs to be of a thin, flexiblematerial such that zero or near zero positive pressure above atmosphericdevelops in compartment 2 as it fills from the Nitric Oxide flow 12during exhalation (so that the valves stay closed while the bag fills).Reservoir 2 thus should be designed preferably to have infinite or nearinfinite Compliance (where Compliance=deltaVolume/deltaPressure), whilefilling—and then drop to zero or near zero Compliance once full.

The first compartment 1 is supplied with an oxygen-containing gasthrough a first inlet port 11, whereas the second compartment 2 forminga NO-reservoir is supplied with a constant flow of NO-containing gasthrough a second inlet port 12.

During patient exhalation, the valves 3 close, so that the secondcompartment or reservoir 2 fills with NO containing gas, whereas, duringpatient inhalation, the valves 3 open so that NO-containing gas mixeswith air and/or oxygen in the first compartment 1 as it is inhaled bythe patient through the prongs 5.

The volume of the second compartment 2 is configured and sized so as tobe small compared to the patient's inhaled tidal volume, so that thesecond compartment 2 quickly empties during the initial period of theinhalation phase to create a bolus of elevated NO concentration at thestart of the inhalation.

Normally high concentrations of NO, e.g. 800 vol. ppm of NO in nitrogen,are delivered to the second compartment 2 from a source of NO/N₂, suchas a gas cylinder with integrated pressure regulator and flow meteringapparatus.

Patient safety is ensured by supplying only low flows of NO-containinggas. For example, to deliver to the patient an amount of NO equivalentto that delivered during continuous supply of gas containing 5 ppmv NOthroughout the duration of a 500 ml tidal breath, about 3 ml of gascontaining 800 ppmv NO should be supplied each breath.

During tidal breathing, the expiratory time of a typical adult willrange from approximately 2 to 5 seconds. Therefore, supply flows on theorder of 1 ml/s of NO containing gas are required. In operation, the NOflow rate may be adjusted based on visual inspection of theinflation/deflation of deformable wall 14 to ensure the appropriate flowrate for a specific patient's inhalation pattern.

FIG. 3 displays an estimated pattern of inhaled NO concentration thatwould be achieved using the present invention based on the numbersmentioned above.

More precisely, one can see on FIG. 3 the estimated tidal flow andinhaled NO concentration curves during a typical adult tidal breathingpattern using a nasal cannula assembly 10 according to the presentinvention supplied with 1 ml/sec flow of gas containing 800 ppmv of NOin N₂.

The breathing pattern is shown in the upper curve, with positive flowrepresenting inhalation, and negative flow representing exhalation. Theestimated NO concentration contained in the gas mixture delivered to thepatient through the nasal prongs 5 during the inhalation phase of thebreathing cycle is shown in the lower curve.

The NO concentration spikes at the start of inhalation as NO-containinggas is released from the second compartment 2 before rapidly decreasingonce the second compartment empties.

Through the later stages of inhalation a low NO concentration isdelivered as fresh NO-containing gas supplied through inlet 12 passesinto the first chamber 1 and the nasal prongs 5.

In contrast, throughout exhalation, flow of NO-containing gas from thesecond chamber to the first chamber is prevented by the valves 3.

For some patients, it may be desirable to minimize gas leaks between thenasal prongs 5 and the patient's nares, e.g. to provide continuouspositive airway pressure CPAP, Bi-level positive airway pressure(Bi-PAP), or other positive pressure support in combination with NOtherapy, or to ensure the proper opening and closing function of thevalves 3.

In such circumstances, the nasal cannula assembly 10 may compriseadditional elements as shown in FIG. 2.

First, each of the nasal prongs 5 includes an external pillow element 8at its ends, which is intended to more tightly secure the prongs 5inside the patient's nares or nostrils. Said pillow elements 8 can bemade of soft resilient material, such as silicone or similar.

Second, an additional one-way expiratory valve 13 is included betweenthe first compartment 1 defining the internal chamber 7 and the roomatmosphere.

Additionally, a resistive element 9 may optionally be placed between theinternal volume 7 of the first compartment 1 and the air or oxygensupply conduit to ensure a sufficient pressure drop upon the onset ofinhalation to open valves 3.

While the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart in light of the foregoing description. Accordingly, it is intendedto embrace all such alternatives, modifications, and variations as fallwithin the spirit and broad scope of the appended claims. The presentinvention may suitably comprise, consist or consist essentially of theelements disclosed and may be practiced in the absence of an element notdisclosed. Furthermore, if there is language referring to order, such asfirst and second, it should be understood in an exemplary sense and notin a limiting sense. For example, it can be recognized by those skilledin the art that certain steps can be combined into a single step.

The singular forms “a”, “an” and “the” include plural referents, unlessthe context clearly dictates otherwise.

“Comprising” in a claim is an open transitional term which means thesubsequently identified claim elements are a nonexclusive listing (i.e.,anything else may be additionally included and remain within the scopeof “comprising”). “Comprising” as used herein may be replaced by themore limited transitional terms “consisting essentially of” and“consisting of” unless otherwise indicated herein.

“Providing” in a claim is defined to mean furnishing, supplying, makingavailable, or preparing something. The step may be performed by anyactor in the absence of express language in the claim to the contrary.

Optional or optionally means that the subsequently described event orcircumstances may or may not occur. The description includes instanceswhere the event or circumstance occurs and instances where it does notoccur.

Ranges may be expressed herein as from about one particular value,and/or to about another particular value. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value and/or to the other particular value, along withall combinations within said range.

All references identified herein are each hereby incorporated byreference into this application in their entireties, as well as for thespecific information for which each is cited.

1. A nasal cannula assembly (10) adapted to deliver gases to a patient,the nasal cannula assembly (10) comprising: a) a hollow body (4)configured to be capable of acting as a gas conduct or a gas manifoldand comprising an internal chamber (7) defining a first compartment (1),b) the first compartment (1) and a second compartment (2) separated by aseparation wall (6), c) a pair of nasal prongs (5) in fluidcommunication with the first compartment (1), d) the first compartment(1) comprising a first inlet (11) forming a side gases entry in fluidcommunication with a gas transport conduct and configured to conduct afirst gas into said first compartment (1), e) the second compartment (2)having a fully inflated internal volume for a gas of about 0.5 to 5 ml,the second compartment (2) comprising, a second inlet (12) configured toconduct a second gas into said second compartment (2), and a deformablewall (14) having a greater Compliance while filling than when the secondcompartment (2) is full, f) the separation wall (6) comprising at leasttwo, one-way, duckbill or umbrella valves (3) having a cracking pressureof 0.5 kPa or less which are oriented and arranged in the separationwall (6) directly opposite the pair nasal prongs (5) to thereby becapable of permitting a passage of gas from the second compartment (2)to the first compartment (1) and preventing or limiting a passage of gasfrom the first compartment (1) to the second compartment (2).
 2. A nasalcannula assembly (10) adapted to deliver gases to a patient, the nasalcannula assembly (10) comprising: a) a first compartment (1) and asecond compartment (2) separated by a separation wall (6), b) a pair ofnasal prongs (5) in fluid communication with the first compartment (1),c) the first compartment (1) comprising a first inlet (11) configured toconduct a first gas into said first compartment (1), d) the secondcompartment (2) comprising a second inlet (12) configured to conduct asecond gas into said second compartment (2), and e) the separation wall(6) comprising at least one valve element (3) configured to permit apassage of gas from the second compartment (2) to the first compartment(1) and prevent or limit a passage of gas from the first compartment (1)to the second compartment (2).
 3. The nasal cannula assembly accordingto claim 1, wherein the separation wall (6) comprises at least two valveelements (3).
 4. The nasal cannula assembly according to claim 1,wherein the first compartment (1) comprises a first inlet (11) forming aside gases entry in fluid communication with a gas transport conduct. 5.The nasal cannula assembly according to claim 1, wherein the nasalcannula assembly further comprises a hollow body (4) comprising aninternal chamber (7) comprising at least the first compartment (1). 6.The nasal cannula assembly according to claim 1, wherein at least thefirst compartment (1) is part of a hollow body (4) configured to becapable of acting as a gas conduct or a gas manifold.
 7. The nasalcannula assembly according to claim 1, wherein said hollow body (4) andsaid pair of nasal prong (5) are integrally molded from a soft plasticsmaterial.
 8. The nasal cannula assembly according to claim 1, whereinthe prongs (5) are detachable from said hollow body (4) and selectedfrom different sized prongs suitable for different sized patient nares.9. The nasal cannula assembly according to claim 2, wherein the twovalve elements (3) are one-way valves.
 10. The nasal cannula assemblyaccording to claim 2, wherein a pair of valve elements (3) is arrangedin the separation wall (6), directly opposite the pair nasal prongs (5).11. The nasal cannula assembly according to claim 1, wherein the secondcompartment (2) comprises a deformable wall (14).
 12. The nasal cannulaassembly according to claim 1, wherein the second compartment (2) formsa deformable-wall reservoir comprising a fully inflated internal volumefor the gas of about 0.5 to 5 ml.
 13. The nasal cannula assemblyaccording to claim 1, wherein nasal cannula assembly does not comprise asensor configured to detect an onset of patient inspiration.
 14. Thenasal cannula assembly according to claim 1, wherein the valve (3) isselected from an umbrella valve or a duckbill valve.
 15. The nasalcannula assembly according to claim 1, wherein the valve (3) has acracking pressure of 0.5 kPa or less.
 16. The nasal cannula assemblyaccording to claim 11, wherein the deformable wall (14) of the secondcompartment (2) has a greater Compliance while filling than when thesecond compartment (2) is full.
 17. The nasal cannula assembly accordingto claim 1, wherein the nasal prongs (5) includes an external pillowelement (8) at an end.
 18. The nasal cannula assembly according to claim16, wherein said pillow elements (8) is made of silicone.
 19. The nasalcannula assembly according to claim 1, further comprising an expiratoryorifice (13), optionally comprising a one-way expiratory valve, betweenthe first compartment (1) defining an internal chamber (7) and anexternal atmosphere.
 20. The nasal cannula assembly according to claim1, further comprising a resistive element (9) between an internal volume(7) of the first compartment (1) and an air or oxygen supply (11), theresistive element configured to ensure a sufficient pressure drop uponthe onset of inhalation to open at least one valve element (3).